The invention relates generally to imaging systems, and more particularly, embodiments relate to an apparatus and method for reducing image artifacts that are produced by movement of an object.
Multi-modality imaging systems exist that scan using different modalities, such as, for example, Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), and Single Photon Emission Computed Tomography (SPECT). During operation, conventional imaging systems may exhibit image quality that is affected by motion of the object being imaged.
Motion of the object being imaged may degrade image quality, for example in medical imaging. More specifically, image artifacts are produced by movement of the object. Respiratory motion is a common source of involuntary motion in mammals (e.g., people and animals) encountered in medical imaging systems. The respiratory motion may lead to errors, such as when a physician is determining the size of a lesion, determining the location of the lesion, or quantifying the lesion.
To correct for motion related imaging artifacts, at least one conventional imaging system utilizes respiratory information. In cases where the data acquisition period is relatively long, conventional imaging systems monitor the patients' breathing using a respiration monitor. The signal generated by the respiration monitor is then used to reduce artifacts in the acquired image data. The conventional motion correction method relies on the assumption that the movement of internal structures in a region of interest is the same over different breathing cycles. However, involuntary motion during respiration may cause a hysteresis effect to occur.
Conventional imaging systems ignore the hysteresis effect resulting in increased motion related artifacts. The hysteresis effect occurs when the movement path followed by the internal structure during inspiration does not coincide with the path followed by the internal structure during expiration. Also, in some cases, the movement of the internal structure may lag behind the respiration signal. For example, deep breathing may cause the internal structure to be at a different position than when shallow breathing is performed. Moreover, if the object breathes faster or slower, the movement of some internal structures may exhibit a delay in reacting to the changes in direction of diaphragm movement.